JP2575473B2 - Aircraft tractor - Google Patents

Abstract

An aircraft towing vehicle has a rearwardly opening recess adapted to receive the nose wheel of an aircraft to be towed. A nose wheel lifting and clamping mechanism has two nose wheel lifters which can be pivoted from a retracted position, in which they are parallel to sides of the vehicle frame, into an operative position, in which they extend into the recess for engaging the aircraft nose wheel. The lifters pivot on rocker arms which themselves pivot about a horizontal axis and are power driven by hydraulic actuators. A separate hydraulic swivel drive motor is provided for each lifter. The pressure increase which takes place when the swivel drive reaches the end of its path is used to initiate the delivery of pressurized fluid to the actuator. A crank arm driven by the hydraulic motor is connected to the support for the lifter with a low back pivot, self locking linkage to positively prevent even excessive forces generated during the nose wheel lifting process from unintentionally moving the lifters towards their retracted positions.

Description

Description: FIELD OF THE INVENTION The present invention relates to a tractor for an airplane, comprising a fork-shaped undercarriage having two side legs surrounding a nose wheel of the airplane, and having a rearward engagement with the nose wheel. A lifting device that lifts the machine collar using two lifting shovels supported on each side leg so as to be able to rotate inward and outward, and each lifting shovel is centered on a substantially vertical axis. The rocker is supported on a rocking body such that the rocking body itself is rotatably supported on a side leg belonging to the chassis so as to be rotatable about a horizontal horizontal axis. From the rest position, projecting about 90 ° from the rest position and for the outward pivoting of the lifting shovel to the working position defined by the stop and for the rotation of the rocker for the subsequent lifting operation. Acts on rocking body And a type provided with a hydraulic drive device having a lifting cylinder.

In a tractor of the above-mentioned type, which is known from DE-OS 3 327 628, a lifting cylinder which acts eccentrically with respect to the pivot axis of the lifting shovel firstly during a first part of the running stroke. Swivel outward,
The rocking body is then rotated so that the lifted lifting shovel can be moved towards the nose collar. In this case, however, the rocker must first be prevented from rotating by the locking means until the lifting shovel is pivoted outward and locked by the pawl in the outward pivoting position. After the lifting shovel has been locked by the pawl, the locking means of the rocker must be released. Upon disengagement of the lifting device, the pawl must be released when the rocker reaches the end of its return path, so that the lifting cylinder pivots the lifting shovel back to the rest position in the last part of its entry stroke. It becomes possible. The actuation or disengagement of the locking means, pawls or the like at the specified point in time, i.e. at the specified point of movement of the movable part, however, requires additional expense and is therefore susceptible to failure, and as a result Dissatisfaction occurs with the operation reliability of the entire device.

SUMMARY OF THE INVENTION It is therefore an object of the invention to improve a tractor of the type mentioned at the outset and to construct a lifting device in such a way that the correct sequence of pivoting and lifting movements of the lifting shovel is forcibly protected by simple means. It is.

Means for Solving the Problems In order to solve this problem, according to the configuration of the present invention, the lifting shovel is pivoted inward and outward around a substantially vertical axis of rotation. Is provided, and the supply of the hydraulic medium to the lifting cylinder is controlled by the pressure increase generated in the swing drive device when the limit stop of the outward swing motion arrives.

Claims 2 and 3 describe another advantageous configuration of the present invention. In this case, according to the configuration of claim 3,
The lifting shovel in the outward pivot position can be easily locked without the need for external engagement.

Embodiment Next, an embodiment of the present invention will be described with reference to the drawings.

The tractor 1 shown schematically in FIG. 1 has a fork-shaped undercarriage with two side legs 3, between which two legs define a rearwardly open undercarriage space 5. The tractor 1 is retracted backwards toward the towed aircraft so that the nose running mechanism of the aircraft enters the cavity 5. The nose of the aircraft is then engaged from behind by means of a lifting device with two lifting shovels 7 and (by a suitable reversing movement of the tractor 1) the forward movement of the lifting shovel causes the nose of the tractor to move. It is lifted until it is supported in the lifted position by the lifting shovel 7 and the ramp 9. In FIG. 1, an additional holding element, which is omitted for clarity of the drawing, acts additionally on the running surface of the nose collar from above, so that the nose collar can escape upwards and upwards. Instead, the tractor 1 is fixed. The tractor 1 and the aircraft thus form a very stable traction connection, which is much more reliable than is possible with a conventional tractor connected via the drawbar of the aircraft. Be able to tow the airplane with gender and especially high speed.

The lifting shovel 7 pivots inward into a rest position in contact with the inner wall of each side leg 3, in order to allow the nose running mechanism of the airplane to enter the tractor cavity 5, and then from behind the nose collar. It can pivot outward to engage.
FIG. 1 shows one lifting shovel 7 in an inward turning position and the other lifting shovel in an outward turning position. To this end, a hydraulic drive, which will be described in detail later, works.

The requirements to be considered in the construction of the lifting device and its hydraulic drive arise on the basis of the intended use of the tractor and the safety considerations to be taken into account. That is, on the one hand, the lifting device is only allowed to have a very small space in the lateral direction of the tractor in the inward turning state, and the inside width of the space 5 needs to be, for example, up to 1.60 m wide. Must be sufficient to accommodate the nose running mechanism of a general-purpose maximum airplane model (for example, Boeing B747). On the other hand, the total width of the tractor is
It must not exceed the maximum value prescribed by the given track of the airfield (actually not exceeding 4.20 m). Thus, only a maximum width of 1.30 m is left for each side leg 3, including the lifting device, and the space required by each rear wheel and its bearings and possibly linking devices. After subtracting, only the maximum width of about 0.3-0.4m remains for the original lifting device. Despite this little available space, the lifting device, of course, must be designed to be strong enough to produce the necessary force to lift the nose collar and the weight of the aircraft applied to the nose collar. No.

Turning now to another aspect, the need to control the movement of a lifting device with as little complicated electronic control as possible, which operates with an electronic position sensor or the like, is not necessary. desirable. It has been found that electronic devices such as the position sensors are very susceptible to failure under rough operating conditions at the airport and due to disturbances due to the proximity of strong electronic light sources and signal sources. The lifting device described below was configured based on the above viewpoints.

According to FIG. 2, in which the lifting device is shown in the inward swiveling position of the lifting shovel, an oscillating body 13 is supported on a slewing bearing 11 having a horizontal axis at the side leg 3 of the tractor. Lifting cylinder on rotary joint 15
17 piston rods are engaged. The other end of the lifting cylinder is mounted on the side leg 3 of the undercarriage at point 19. A shaft 22 of a lifting shovel support 23 is rotatable on a bearing sleeve 20 having an axis 21 which is located substantially vertically on the rocking body 13 (inclined substantially forward in the position shown in FIG. 2). It is supported and the lifting shovel support 23 supports the original lifting shovel 7. Lifting shovel 7
It is designed as a roll platform with a plurality of rolls 27 parallel to one another, the lower five rolls being located on a frame 29 pivotally mounted on the lifting shovel 7. In this way, the lower part of the lifting shovel 7 can be adapted to different dimensions of the wing collar of the airplane to be gripped in each case.

Further, the entire lifting shovel in the lifting shovel support 23 is supported so as to be tiltable about an axis 36 perpendicular to the axis 21.
A tilting movement controlled by a link mechanism, not shown, can be performed to engage the nose collar from below.

Lifting shovel support centered on vertical pivot axis 21
The swiveling motion of the lifting shovel 7 and the lifting shovel 7
This is generated by a hydraulic swing motor 31 fixed to the motor. The rotation axis of the turning motor 31 is located parallel to the turning axis 21. A crank arm 33 is fixed to the shaft of the hydraulic torque motor 31 so as not to rotate.
The crank arm 33 is pivotally connected to a swing arm 37 of the lifting shovel support 23 via a connection link 35. In particular, as can be seen from the upper part of FIG. 4, the fixed pivot axis 21 and the fixed axis of the pivot drive device 31 and the pivot joint axis 34 or the coupling link 35 between the crank arm 33 and the coupling link 35 pivot. The rotary joint axis 36 with the arm 37 forms a four-point link transmission.

In the inward swiveling position of the lifting shovel 25 shown in the upper part of FIG. A limit stop that determines the position is formed. Further rotation in the counterclockwise direction is no longer possible. When the hydraulic medium is supplied to the hydraulic torque motor 31, the torque motor rotates the crank arm 33 clockwise in the upper half of FIG. In this intermediate position, the crank arm has moved, for example, to position 33 'and the lifting shovel has moved to position 7'. The crank arm 33 moves a turning distance of 180 degrees or more in the clockwise direction,
Until it comes into contact with the limit stopper 39 of the oscillator 13,
A hydraulic medium is further supplied to the torque motor 31. 4th
In the position of the crank arm 33 shown in the lower part of the figure,
The link 35 pivots the lifting shovel support 23 and the lifting shovel 7 to a complete outward pivoting position 90 ° away from the side legs 3. During the pivoting movement formed by the longitudinal axis of the crank arm 33 and the connecting link 35, the angle which always becomes smaller initially reaches the value 0 before the crank arm 33 reaches the limit stop 39 and the remaining pivoting movement. Sometimes the longitudinal axis of the connecting link 35 moves beyond the longitudinal axis of the crank arm 33, for example, the longitudinal axis of the connecting link changes from one side to the other. As a result, the lifting shovel 7 is mechanically locked against the inward turning in the outward turning position (see the lower part of FIG. 4). The force acting on the lifting shovel in the direction of arrow 41, that is, the force applied during the engagement and lifting from behind the airplane's collar does not cause the lifting shovel 7 to pivot. This is because the torque transmitted to the crank arm 33 via the connecting arm 5 by such a force has a direction such that the crank arm 33 is pressed against the limit stopper 39. In addition, the connecting link 35 may also have a shape on its inner side such that the connecting link 35 is always lifted and kept in contact with the side surface of the shovel 23.

In the following, the mode of operation of the device will be described with reference to the simplified hydraulic circuit diagram shown in FIG. In FIG. 5, the hydraulic conduit is shown by a solid line and the signal wire is shown by a broken line. Lift cylinders 17 on both sides of the aircraft as hydraulic actuators
And the torque motor 31 are symbolically shown. The hydraulic pressure is
It is fed to a pressure line 47 from a supply system having a storage tank 51, a pump 43 and possibly an accumulator 45. The drain conduit 49 communicates with the tank 52.

An electric valve 55 operated by a tractor driver using a lever 53 can selectively connect the two hydraulic lines 57,59 with the pressure line 47 and the drain line 49 or vice versa. FIG. 5 shows the position of the valve 55 for the lifting operation, that is, the position of the valve 55 for the inward turning of the lifting shovel 25 and the subsequent forward movement. The movement of the valve 55 to this position, the release of the lifting movement, can be performed in relation to how close the tractor has been to the nose of the aircraft. That is, when the noseplate comes into contact with the climbing ramp 9 (see FIG. 1) schematically shown in FIG. 5 which is supported to be tiltable, and the climbing ramp 9 is tilted downward, the operation is performed via the relay 62. The limit switch 61 for opening the valve 55 is operated. In the position shown, the hydraulic medium reaches the torque motor 31 via the conduits 47, 57, whereby the torque motor is driven and the associated lifting shovel 7 is moved from the rest position shown in FIG. 2 to FIG. Swivel to indicated operating position. During this operation, the pressure in the conduit 57 is smaller than the opening pressure of the pressure switching valve 63 that shuts off the supply of the hydraulic medium from the conduit 57 to the lifting cylinder 17. During operation of the torque motor 31, the hydraulic medium can flow out of the torque motor via the check valve 65 and the conduits 59,49.

When the torque motor 31 reaches the end of its rotary movement path, that is, when the crank arm 33 reaches the stop 39 (FIG. 4), the oil pressure in the conduit 57 increases, and as a result, the pressure switching valve 63 opens and lifts. A cylinder 17 is supplied with hydraulic medium to the piston-side working chamber, whereby the piston is moved out to move the lifting shovel 7 forward about a horizontal pivot 11. At this time, the hydraulic medium can flow out of the working chamber on the piston rod side of the lifting cylinder 17 via the conduits 59 and 49. During this lifting movement, the nose of the airplane is pushed forward by the lifting ramp 9 from the lifting shovel 7 and the lifting point moves beyond the tilt axis 10 of the lifting ramp 9. Tilt forward and operate another limit switch 67. Signal of this Rimitsutosuitsuchi reaches the switching Yunitsuto 17, the switching Yunitsuto actuates the desired frettage pressure P pressure switch 73 which is adjusted to _E defined. Finally, the nose collar reaches the limit stop, making it impossible to move any further.
The pressure at increases strongly. As soon as the pressure switch 69 is obtained a final pressure P _E is responsive, at the same time switches 67,73
The end of the lifting operation is indicated by the presence of a signal from the switching unit 71, whereby the switching unit 71 gives a different command to another part of the lifting system, for example, the presser body. Lifting cylinder 17 remains had it occurred in the load on frettage pressure P _E of the provisions obtained at the end of the lifting operation, which can be by connexion guaranteed actively locking releasable check valve 69, for example.

Each lifting cylinder can have a locking device 75 for clamping the piston rod in the respective run-out position. Such piston rod clamping devices are known per se and are on the market. Such a device consists, for example, of a disc spring unit, which is capable of contacting and clamping the piston rod unless it is released from the piston rod by the load of a hydraulic medium. it can. Thus, the locking of the piston rod is always automatically effective, unless it is kept open by active unlocking by the hydraulic medium.
During the lifting operation released by the lever 53, the locking device 75 is kept open via the hydraulic conduit 77. Lifting the operation is terminated by the lifting cylinder is loaded with a desired frettage pressure P _E, the piston rod lock is machine collar lifting cylinder 17, the coercive the clamping state, even if the pressure drops in the example, a hydraulic system Dripping.

The operations are performed in a substantially reverse order for releasing and lowering the nose collar. With the aid of a lever 53 which can be operated by a driver, the valve 55 is brought into a position in which the pressure line 47 is connected to the line 59 and the drain line 49 is in contact with the line 57. The hydraulic medium reaches via a conduit 59 the working chamber on the piston rod side of the lifting cylinder 17, whereby the lifting shovel on the tractor is moved backwards, so that the nose wheel is lowered via the lifting ramp 9. Let me do. The hydraulic medium from the working chamber on the piston side is then supplied to the check valve 76 and conduits 57,4
Leaked through 9. During this operation, the pressure in the conduit 59 and the lifting cylinder 17 is lower than the opening pressure of the pressure switching valve 79 that shuts off the supply of the hydraulic medium to the torque motor 31. During the lowering operation, the lifting shovel is therefore in its outer pivot position in the lever arms 33, 35 shown in FIG.
Is locked based on the geometric shape of the

When the lifting cylinder 17 reaches the end of its return stroke,
The pressure in the conduit 59 increases, the pressure switching valve 79 opens, and hydraulic medium is supplied to the torque motor 31. As a result, the torque motor rotates, and the lifting shovel 7 turns from the working position shown in FIG. 3 to the rest position shown in FIG.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a tractor according to the present invention,
2 is a side view showing the lifting shovel device in the inward turning position, FIG. 3 is a side view showing the lifting shovel device in the outer turning position, and FIG. 4 is an inward turning position and an outward turning of the lifting shovel device. FIG. 5 is a schematic view showing a hydraulic circuit of the lifting device. 1 ... tractor, 3 ... side legs, 5 ... undercarriage, 7 ...
Lifting shovel, 9 ... Ramp ramp, 10 ... Tilt axis,
11 ... Slewing bearing, 13 ... Oscillator, 15 ... Rotating joint, 17 ... Lifting cylinder, 19 ... Part, 20 ... Bearing sleeve, 21 ... Slewing axis, 22 ... Shaft, 23 ... Lifting Shovel support, 27 roll, 29 frame, 31 torque motor (slewing drive), 33 crank arm,
34 ... rotating joint shaft, 35 ... connecting link, 36 ... axis, 37 ... revolving arm, 39 ... limit stop, 41 ...
… Arrows, 43 …… pumps, 45 …… accumulators, 47 ……
Pressure conduit, 49… Drain conduit, 51… Storage tank, 52…
... Tank, 53 ... Lever, 55 ... Valve, 57,59 ... Hydraulic conduit, 61 ... Limit switch, 62 ... Relay, 63 ... Pressure switching valve, 67 ... Limit switch, 69 ... Press switch (reverse) Stop valve), 71 ... switching unit, 73 ... pressure switch, 75 ... locking device, 77 ... pressure conduit, 79 ... pressure switching valve.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-164899 (JP, A) WO 87/6910 (WO, A)

Claims (3)

(57) [Claims] 1. A tractor for an airplane, comprising a fork-shaped undercarriage having two side legs surrounding a nose collar of the airplane, a rearward engagement with the nose collar, and an inward turning and an outward turning on each side leg. A lifting device that lifts the nose collar using two lifting shovels that are rotatably supported,
Each lifting shovel is supported on an oscillating body so as to be pivotable about a substantially vertical axis, and the oscillating body itself is supported on side legs belonging to the chassis so as to be rotatable about a horizontal horizontal axis. In this case, from the rest position in contact with the side legs and swiveling, the lifting shovel projects approximately 90 ° from the rest position and to the working position defined by the stopper, and then goes out for turning. A lifting device which is provided with a hydraulic drive device having a lifting cylinder acting on the rocking body for the rotation of the rocking body for the lifting operation to be carried out, wherein the lifting around a substantially vertical axis of rotation (21) is carried out For the inward and outward turning of the shovel, a unique hydraulic turning drive (31) is provided which is separated from the lifting cylinder (17) and turns when the limit stop of the turning movement reaches. And wherein the and summer as Yotsute the pressure increase occurring in the driving apparatus, the supply of hydraulic medium lifting the cylinder (17) is controlled, tractor airplane. 2. The tractor according to claim 1, wherein the hydraulic turning drive (31) is a hydraulic torque motor. The torque motor (31) is connected to a connecting link (35).
The crank arm (33), which is connected to the swing arm (37) of the lifting shovel (7) via the arm, is operated in this case, the arm length and the swing path are such that the crank arm (33) is connected to the limit stop (39). 3. The connecting link (35) is set to change from one side of the crank arm axis to the other before reaching the end of the pivot path of the crank arm (33) thus determined. Tractor.